In the field of automatic dishwashing the formulator is constantly looking for improved and simplified cleaning compositions and methods. There is a need for finding compositions having a more environmentally friendly profile, i.e. using more environmentally friendly ingredients, reducing the number of ingredients, reducing the amount needed for achieving good cleaning and being more effective than current compositions.
Cleaning compositions comprising nanoparticles are known in the art. Nanoparticles present serious stability issues when placed in a wash liquor (aqueous medium). Nanoparticles have a substantial fraction of their atoms or molecules at the surface. When placed in an aqueous medium, an interface exists between the surface of the particles and the carrier liquid. The behaviour of the resultant dispersion, including stability, is mainly determined by how this surrounding interface interacts with the surface of the nanoparticles and the carrier liquid.
Solutions, unlike nanoparticulate dispersions or suspensions, lack an identifiable interface between their solubilized molecules and the solvent. In solutions, the solubilized molecules are in direct contact with the solvent, while in dispersions only the surface of the nanoparticles are in direct contact with the carrier liquid. Hence, the carrier liquid does not solubilize the particles that make up a dispersion; instead, the carrier liquid “carries” the particles; by carrying the particles, a suspension or dispersion results. The terms “suspension” and “dispersion” are herein used interchangeably.
The interfaces between the suspended nanoparticles, and the carrier liquid or liquid mixture in which they reside, play a dominant role in determining the behaviour and capabilities of the nanoparticle dispersion. Suspensions are considered stable if the nanoparticles are separated or deflocculated, i.e., not aggregated or flocculated.
An objective of the present invention is to provide a cleaning composition comprising nanoparticles capable of forming a stable dispersion in a cleaning medium (or wash liquor), preferably in an aqueous wash liquor. The terms “cleaning medium” and “wash liquor” are herein used interchangeably.
Another problem related to compositions comprising nanoparticles is that the nanoparticles can interact with other components of the composition in the aqueous cleaning medium, thereby reducing its cleaning activity. This interaction is particularly detrimental in the case of protease enzymes. Thus another objective of this invention is to provide cleaning compositions comprising nanoparticles and at the same time having a high protease activity.